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CHAPTER 9: FUNGAL GENETICS, MOLECULAR GENETICS AND GENOMICS

Chapter 9 is divided into the following major sections:

overview: the place of fungi in genetical research
Neurospora and classical (Mendelian) genetics
structure and organisation of the fungal genome
genetic variation in fungi
applied molecular genetics of fungi
Returning to the genome
expressed sequence tags and microarray technology

SAMPLE TEXT:

In this chapter we cover the basic and applied genetics of fungi, including the features that continue to make fungi important model organisms for genetical research. The chapter includes recent molecular approaches in a range of fields such as the analysis of fungal pathogenicity determinants and the development of fungi as ‘factories’ for foreign gene products. It also covers the roles of extrachromosomal genes in ageing-related senescence and the effects of fungal viruses (hypoviruses) in suppressing pathogenic virulence.

Fungi are eminently suitable for biochemical studies because of their simple nutrient requirements, and because ‘classical genetics’ has provided excellent physical maps of the chromosomal genes. Studies on one fungus in particular – Neurospora crassa – led to the classical concept of ‘one gene, one enzyme’, for which Beadle & Tatum (1945) received the Nobel Prize. However, with more recent knowledge it is more accurate to say that ‘one gene can encode one enzyme’ – the situation is complicated because gene splicing occurs to remove non-coding introns in the pre-messenger RNA.

At the time of writing (May 2004), the genomes of nearly 150 organisms have been sequenced – mainly bacteria and archaea, but also the genomes of mouse and ‘man’. Notably in our present context, the ‘high-quality draft’ genome sequences of five fungi have been published – Saccharomyces cerevisiae, Neurospora crassa, Emericella (Aspergillus) nidulans, Schizosaccharomyces pombe and the rice blast pathogen, Magnaporthe grisea. The first four of these are Ascomycota with well-mapped chromosomes, providing a basis for combining classical and molecular genetics.

Chapter 9 images. Click on thumbnails
Fig. 9.1 Fig. 9.8 Fig. 9.10 Fig. 9.14	Fig. 9.2 Fig. 9.5 Fig. 9.11 Fig. 9.15	Fig. 9.3 Fig. 9.6 Fig. 9.12 Fig. 9.16	Fig. 9.4 Fig. 9.7 Fig. 9.9 Fig. 9.13 [see text for Figs 9.17 and 9.18]

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